Previously in building wall assemblies including an outer veneer wall, a series of laterally spaced studs upon one side thereof and spaced from said wall and wherein upper and lower sets of wall boards span the respective studs, there has been the problem of preventing the accumulated moisture upon the upper wall boards from entering into the interior of the lower wall boards and for communication into the space between the studs and any interior room adjacent thereto. Various efforts have been made to prevent such accumulating moisture from passing through the lower wall boards and into a building assembly.